Competition Between Different Nitrogens

Efficient epoxidation of a variety of linear and cyclic alkenes by RuClj/aq. Na(IO )/(bpy)/CH2CyO-5°C/15 h was observed [735] 5-methyl- or 3,4,7,8-tetram-ethyl-phenanthroline can replace (bpy) [736], The active species when (bpy) is present is probably franx-Ru(0)2(bpy) 103(011)3 [567, 568], Competition between epoxidation and cleavage of fran -stilbene with bidentate ligands (pyridine, oxazo-line, oxazolidine and thiophene), containing two different nitrogen heterocycles either linked or separated by a spacer together with RuCyaq. Na(IO )/CH3Cy2°C was reported [737],... 

Figure 30.3 Difference between nitrogen uptake and growth kinetics from experiments, after Zehr et al. (1988). Short-term uptake kinetics (A) are driven by membrane transport processes, and usually exceed assimilation and incorporation into protein. Short-term uptake declines as feedback from internal pools and regulatory mechanisms are affected by influx of N. (B) Longer term N uptake is driven by protein synthesis rate, which is equivalent to the growth rate. (C) Model of competition between two species showing that competition can be affected by both transport and growth.

The morphological and physiological dissimilarities between mycorrhizal symbi-o.ses probably determine their success and their distinct patterns in different ecosystems (92). Nitrogen (N) available to both AM and ectomycorrhizal plants should not be regarded as a single pool open to free competition. Specialization of its acquisition and utilization in a given habitat is an important feature of plant and microbial community structure, while the fact that the ability to exploit its sources (and tho.se of other limited nutrients) is not the same in all species may result in niche differentiation (93). If habitat specialization is a reflection of differences between mycorrhizal types, ectomycorrhizal and AM species could cooccur because they exploit different niches in the. same ecosystem. 

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